The present invention relates to a heel securing device, particularly for rear-entry ski boots.
It is currently known that a problem to be solved in the manufacture of ski boots, in particular rear-entry ski boots, is that of correctly securing the skier's heel.
However, due to the particular structure of such boots, the ankle is necessarily allowed a certain play within the shell. This play limits the skier's sensitivity when transmitting to the ski the forces generated during the bending and stretching movements occurring during skiing.
As a partial solution to these disadvantages, U.S. Pat. No. 4,615,127, is known wherein a screw mounted on the rear quarter is adapted to cause plates or rigid blocks to interact with a flap protruding from the heel region of the shell.
Such a solution, however, is not devoid of disadvantages: first of all the plates or blocks are rigid and therefore difficult to adapt to the anatomical morphology of the foot, and they furthermore act on a small region of the flap at the heel region of the shell, causing concentrated points of localized pressure.
Known from German patent No. 2732522 is a ski boot having rigid side panels rearwardly separated by a U-shaped notch, and a bridge piece having inwardly pointing extensions engageable in vertical holes formed in the boot adjacent the U-shaped notch, for detachably fixing the bridge piece thereon, so as to adapt the ankle portion of the boot to the anatomical morphology of a skier's ankle.
However, while such an arrangement may be satisfactory for adjusting the fit of the upper cuff of a boot at the ankle region, it has the disadvantage that it does not permit the wearer's heel to be secured within the boot since it does not act on the heel region. Furthermore, tightening of the bridge piece contracts the ankle region of the boot. This can cause difficulty when putting on and taking off the boot, and may constitute a source of discomfort during skiing.
Known from U.S. Pat. No. 2,935,798 is a ski boot having a pair of rigid blades defining fore ends riveted to opposite external sides of the shell below the instep, and rear ends which are drawn together by a tightener above the ball of the heel with resultant deformation of the heel region of the boot shell.
While such an arrangement could be adopted with shells or uppers made of leather or similar flexible material, it would not be suitable in modern ski boot construction employing a rigid heel portion designed to protect the skier's heel, which could not readily transmit pressure from the tightened blades to the skier's foot. Furthermore, such blades located at the exterior of the shell can easily be damaged and may even constitute a safety hazard in the case of a fall since they may become entrapped or entangled and cause injury to the skier. Such blades are also extremely awkward to tighten while the boot is being worn, create difficulty regarding putting on the boot if tightened before being worn, and lead to damage of the shell through the deformation necessarily caused when tightened.
As a partial solution to such problems, U.S. Pat. No. 4,160,332 teaches a ski boot having a shell surrounding the foot and the front of the tibia, a rear spoiler hinged to the shell, and a device for applying pressure to the instep through a distributor plate which is actuated by closing the spoiler onto the shell. Although such an arrangement has proved to be effective for securing the instep portion or fore-part of the foot within the boot, it does not solve the problem of how to prevent a skier's heel from shifting when performing forward stretching movements during skiing.
Thus, such known types of ski boot do not permit maximum sensibility in transmission of the skier's movements to the ski to be maintained at all times. Frequently, skiers possessing such known types of boots often make resort to excessively tightening instep pressers to force the heel towards the lower heel region of the boot, but even such excessive tightening does not always prevent the heel from shifting upwardly when stretching forwards, and often causes discomfort due to the excessive pressure exerted on the foot in such an attempt to secure the heel.
As a partial solution to these disadvantages, U.S. Pat. No. 4,724,625 of Feb. 16, 1988 by the same applicant discloses a ski boot particularly of the rear-entry type comprising an elongate element extending transversely to the longitudinal extension of the rear quarter of the ski boot, said elongate element being provided inside the rear quarter substantially at the heel of the user's foot and being connected to the opposite longitudinal edges of the rear quarter.
Though said elongate element allows uniform distribution of forces at the flap, it does not permit optimum securing of the skier's heel when stretching during skiing, since the degree of rotation of the rear quarter is less than the degree of rotation of the front quarter.
Should the skier wish to tighten the elongate element in order to compensate for this disadvantage when stretching during skiing, another disadvantage arises due to the difficulty encountered when inserting the foot into and extracting the foot from the boot, since the elongate element, when so-tightened, hinders backward movement of the flap protruding from the shell at the heel region.